function variance(m,v,n)
%function variance(m,v,n)
%
% m = mean
% v = variance
% n: extend

X=-n:1:n;
L=length(X);

for i=1:L
    
    P(i)= exp(-0.5*((X(i)-m).^2)/v);
    
end

P = P ./ sum(P);

figure;
bar(X,P);
drawnow;

EX = sum(X.*P)
EXX = sum(((X-EX).^2).*P)
STD = sqrt(EXX)